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Journal of Environmental Sciences... Apr 2021The emissions of NO and HONO from the KNO photolysis in the presence of TiO were measured using a round-shape reactor coupled to a NO analyzer. TiO played important...
The emissions of NO and HONO from the KNO photolysis in the presence of TiO were measured using a round-shape reactor coupled to a NO analyzer. TiO played important roles in the emission flux density of NO (R) and HONO (R), depending on crystal structures and mass ratios of TiO. R and R significantly decreased with increasing the rutile and anatase mass ratios from 0 to 8 and 0.5 wt.%, respectively. Nevertheless, with further increasing the anatase mass ratio to 8 wt.%, there was an increase in R and R. R on KNO/TiO/SiO had positive correlation with the KNO mass (1-20 wt.%), irradiation intensity (80-400 W/m) and temperature (278-308 K), while it had the maximum value at the relative humidity (RH) of 55%. R on KNO/TiO/SiO slightly varied with the KNO mass and temperature, whereas it increased with the irradiation intensity and RH. In addition, the mechanism for NO and HONO emissions from the nitrates photolysis and atmospheric implications were discussed.
Topics: Nitrates; Nitrogen Dioxide; Nitrous Acid; Photolysis; Silicon Dioxide; Titanium
PubMed: 33637244
DOI: 10.1016/j.jes.2020.09.016 -
Unveiling the Mechanism of Photodamage to Sphingolipid Molecules via Laser Flash Photolysis and EPR.Photochemistry and Photobiology 2023Sphingolipids are involved in the maintenance of the skin barrier function and regulate cellular processes of keratinocytes. The work reported here is designed to...
Sphingolipids are involved in the maintenance of the skin barrier function and regulate cellular processes of keratinocytes. The work reported here is designed to uncover details of the mechanism of damage to such lipids by UV radiation. Our approach employs laser flash photolysis and electron paramagnetic resonance (EPR) spectrometry to explore the mechanism of the decay reactions, and to determine the associated kinetic parameters. To interpret our experiments, we computed both excitation energies and EPR parameters of radicals formed during photolysis. Employing the spin-trap EPR method confirmed the formation of both carbon- and nitrogen-centered radicals. Thus, we can conclude that the photodecomposition of sphingolipids and their analogues proceeds by Norrish type I reactions with the formation of both nitrogen-centered and alkyl radicals.
Topics: Electron Spin Resonance Spectroscopy; Photolysis; Lasers; Nitrogen; Free Radicals
PubMed: 36943199
DOI: 10.1111/php.13804 -
International Journal of Molecular... Oct 2023Graphitic carbon nitride (g-CN), a metal-free polymer semiconductor, has been recognized as an attractive photocatalytic material for environmental remediation because... (Review)
Review
Graphitic carbon nitride (g-CN), a metal-free polymer semiconductor, has been recognized as an attractive photocatalytic material for environmental remediation because of its low band gap, high thermal and photostability, chemical inertness, non-toxicity, low cost, biocompatibility, and optical and electrical efficiency. However, g-CN has been reported to suffer from many difficulties in photocatalytic applications, such as a low specific surface area, inadequate visible-light utilization, and a high charge recombination rate. To overcome these difficulties, the formation of g-CN heterojunctions by coupling with metal oxides has triggered tremendous interest in recent years. In this regard, zinc oxide (ZnO) is being largely explored as a self-driven semiconductor photocatalyst to form heterojunctions with g-CN, as ZnO possesses unique and fascinating properties, including high quantum efficiency, high electron mobility, cost-effectiveness, environmental friendliness, and a simple synthetic procedure. The synergistic effect of its properties, such as adsorption and photogenerated charge separation, was found to enhance the photocatalytic activity of heterojunctions. Hence, this review aims to compile the strategies for fabricating g-CN/ZnO-based Z-scheme and S-scheme heterojunction photocatalytic systems with enhanced performance and overall stability for the photodegradation of organic pollutants. Furthermore, with reference to the reported system, the photocatalytic mechanism of g-CN/ZnO-based heterojunction photocatalysts and their charge-transfer pathways on the interface surface are highlighted.
Topics: Zinc Oxide; Photolysis; Oxides; Environmental Pollutants
PubMed: 37834469
DOI: 10.3390/ijms241915021 -
Journal of the American Chemical Society Jul 2022Photolabile protecting groups (PPGs) enable the precise activation of molecular function with light in many research areas, such as photopharmacology, where remote...
Photolabile protecting groups (PPGs) enable the precise activation of molecular function with light in many research areas, such as photopharmacology, where remote spatiotemporal control over the release of a molecule is needed. The design and application of PPGs in recent years have particularly focused on the development of molecules with high molar absorptivity at long irradiation wavelengths. However, a crucial parameter, which is pivotal to the efficiency of uncaging and which has until now proven highly challenging to improve, is the photolysis quantum yield (QY). Here, we describe a novel and general approach to greatly increase the photolysis QY of heterolytic PPGs through stabilization of an intermediate chromophore cation. When applied to coumarin PPGs, our strategy resulted in systems possessing an up to a 35-fold increase in QY and a convenient fluorescent readout during their uncaging, all while requiring the same number of synthetic steps for their preparation as the usual coumarin systems. We demonstrate that the same QY engineering strategy applies to different photolysis payloads and even different classes of PPGs. Furthermore, analysis of the DFT-calculated energy barriers in the first singlet excited state reveals valuable insights into the important factors that determine photolysis efficiency. The strategy reported herein will enable the development of efficient PPGs tailored for many applications.
Topics: Cations; Coumarins; Photolysis
PubMed: 35775744
DOI: 10.1021/jacs.2c04262 -
Journal of Agricultural and Food... Aug 2018Photodegradation of a new strobilurin fungicide, mandestrobin, was investigated in buffered aqueous solution and synthetic humic water (SHW) under continuous irradiation...
Photodegradation of a new strobilurin fungicide, mandestrobin, was investigated in buffered aqueous solution and synthetic humic water (SHW) under continuous irradiation with artificial sunlight (λ > 290 nm). In both aquatic media, the direct photolysis preferentially proceeded via homolytic bond cleavage at the benzyl phenyl ether, and the subsequent recombination of geminate radicals in a solvent cage gave the photo-Claisen rearrangement products. A radical mechanism in the photochemical rearrangement was strongly supported by a radical-trapping technique using a novel nitroxide spin label combined with electron spin resonance (ESR) and liquid chromatography-mass spectrometry (LC-MS) analyses. Photosensitized generation of hydroxyl radical in SHW might significantly contribute to enhancing the formation of a benzyl alcohol derivative. The series of photolysis products steadily degraded and finally mineralized to carbon dioxide.
Topics: Chromatography, Liquid; Electron Spin Resonance Spectroscopy; Fungicides, Industrial; Kinetics; Photolysis; Strobilurins; Sunlight; Tandem Mass Spectrometry; Water Pollutants, Chemical
PubMed: 30049214
DOI: 10.1021/acs.jafc.8b03610 -
Environmental Pollution (Barking, Essex... May 2023In the present work, we constructed a serials of novel shaddock peel-derived N-doped carbon quantum dots (NCQDs) coupled with BiOBr composites. The result showed that... (Review)
Review
Shaddock peel-derived N-doped carbon quantum dots coupled with ultrathin BiOBr square nanosheets with boosted visible light response for high-efficiency photodegradation of RhB.
In the present work, we constructed a serials of novel shaddock peel-derived N-doped carbon quantum dots (NCQDs) coupled with BiOBr composites. The result showed that the as-synthesized BiOBr (BOB) was composed of ultrathin square nanosheets and flower-like structure, and NCQDs were uniformly dispersed on the surface of BiOBr. Furthermore, the BOB@NCQDs-5 with optimal NCQDs content displayed the top-flight photodegradation efficiency with ca. 99% of removal rate within 20 min under visible light and possessed excellent recyclability and photostability after 5 cycles. The reason was attributed to relatively large BET surface area, the narrow energy gap, inhibited recombination of charge carriers and excellent photoelectrochemical performances. Meanwhile, the improved photodegradation mechanism and possible reaction pathways were also elucidated in detail. On this basis, the study opens a novel perspective to obtain a highly efficient photocatalyst for practical environment remediation.
Topics: Photolysis; Quantum Dots; Carbon; Catalysis; Light
PubMed: 36906054
DOI: 10.1016/j.envpol.2023.121424 -
Environmental Science and Pollution... Mar 2024Bendazone (BNTE) is an herbicide and a highly concerned pollutant in aquatic environments. Understanding the photochemical behavior of BNTE in water is crucial for...
Bendazone (BNTE) is an herbicide and a highly concerned pollutant in aquatic environments. Understanding the photochemical behavior of BNTE in water is crucial for evaluating its photochemical conversion process in aquatic environments. This study analyzed the direct photolysis and indirect photolysis pathways of two dissociated forms of BNTE in water through density functional theory and time-dependent density functional theory method. The results show that the reaction types of indirect photolysis of BNTE with free radicals (•OH, •SO, and •CO) are OH addition, SO addition, and CO addition. In the process of indirect photolysis of BNTE and free radicals, the photolysis of •OH and BNTE was the easiest, followed by •SO. In addition, the active site of BNTE reacting with •OH is C8, and the active site of BNTE reacting with •SO is C10. However, the photolysis effect of •CO on BNTE is very small, indicating that •CO in water plays a secondary role in the indirect photolysis of BNTE. In the direct photolysis of BNTE, N1-C6 bond breaking is difficult to occur spontaneously in the environment due to its high endothermic property and energy barrier. The direct photolysis pathway of BNTE involves the break of the N1-S2/S2-N3/N3-C12 bond. In addition, the ecological toxicity evaluation showed that toxicity of most of the degradation products were reduced, but the toxicity level was still maintained at a harmful level. Our findings provide the photochemical fate of BNTE in aquatic environments and will help to more accurately understand their photochemical conversion mechanisms in the environment.
Topics: Photolysis; Water; Water Pollutants, Chemical; Kinetics; Free Radicals
PubMed: 38353814
DOI: 10.1007/s11356-024-32315-z -
Physical Chemistry Chemical Physics :... Sep 2016Photophysical investigations of the canonical nucleobases that make up DNA and RNA during the past 15 years have revealed that excited states formed by the absorption of... (Review)
Review
Photophysical investigations of the canonical nucleobases that make up DNA and RNA during the past 15 years have revealed that excited states formed by the absorption of UV radiation decay with subpicosecond lifetimes (i.e., <10(-12) s). Ultrashort lifetimes are a general property of absorbing sunscreen molecules, suggesting that the nucleobases are molecular survivors of a harsh UV environment. Encoding the genome using photostable building blocks is an elegant solution to the threat of photochemical damage. Ultrafast excited-state deactivation strongly supports the hypothesis that UV radiation played a major role in shaping molecular inventories on the early Earth before the emergence of life and the subsequent development of a protective ozone shield. Here, we review the general physical and chemical principles that underlie the photostability, or "UV hardiness", of modern nucleic acids and discuss the possible implications of these findings for prebiotic chemical evolution. In RNA and DNA strands, much longer-lived excited states are observed, which at first glance appear to increase the risk of photochemistry. It is proposed that the dramatically different photoproperties that emerge from assemblies of photostable building blocks may explain the transition from a world of molecular survival to a world in which energy-rich excited electronic states were eventually tamed for biological purposes such as energy transduction, signaling, and repair of the genetic machinery.
Topics: DNA; Electron Transport; Nucleotides; Photolysis; RNA; Ultraviolet Rays
PubMed: 27539809
DOI: 10.1039/c6cp04230a -
Journal of Agricultural and Food... Mar 2018Dicloran appears to be a model pesticide for investigating photodegradation processes in surface waters. Photodegradation processes are particularly relevant to this...
Dicloran appears to be a model pesticide for investigating photodegradation processes in surface waters. Photodegradation processes are particularly relevant to this compound as it is applied to crops grown in proximity to freshwater and marine ecosystems. The photodegradation of dicloran under simulated sunlight was measured in distilled water, artificial seawater, phosphate buffer, and filter-sterilized estuarine water to determine its half-life, degradation rate, and photodegradation products. The half-life was approximately 7.5 h in all media. There was no significant difference in the rate of degradation between distilled water and artificial seawater for dicloran. For the intermediate products, a higher concentration of 2-chloro-1,4-benzoquinone was measured in artificial seawater versus distilled water, while a slightly higher concentration of 1,4-benzoquinone was measured in distilled water versus artificial seawater. The detection of chloride and nitrate ions after 2 h of light exposure suggests photonucleophilic substitution contributes to the degradation process. Differences in product distributions between water types suggest that salinity impacts on chemical degradation may need to be addressed in chemical exposure assessments.
Topics: Aniline Compounds; Fresh Water; Half-Life; Pesticides; Photolysis; Seawater; Sunlight; Water Pollutants, Chemical
PubMed: 29474091
DOI: 10.1021/acs.jafc.8b00211 -
Electroporation loading and flash photolysis to investigate intra- and intercellular Ca2+ signaling.Cold Spring Harbor Protocols Mar 2015Many cellular functions are driven by variations in the intracellular Ca(2+) concentration ([Ca(2+)]i), which may appear as a single-event transient [Ca(2+)]i elevation,...
Many cellular functions are driven by variations in the intracellular Ca(2+) concentration ([Ca(2+)]i), which may appear as a single-event transient [Ca(2+)]i elevation, repetitive [Ca(2+)]i increases known as Ca(2+) oscillations, or [Ca(2+)]i increases propagating in the cytoplasm as Ca(2+) waves. Additionally, [Ca(2+)]i changes can be communicated between cells as intercellular Ca(2+) waves (ICWs). ICWs are mediated by two possible mechanisms acting in parallel: one involving gap junctions that form channels directly linking the cytoplasm of adjacent cells and one involving a paracrine messenger, in most cases ATP, that is released into the extracellular space, leading to [Ca(2+)]i changes in neighboring cells. The intracellular messenger inositol 1,4,5-trisphosphate (IP3) that triggers Ca(2+) release from Ca(2+) stores is crucial in these two ICW propagation scenarios, and is also a potent trigger to initiate ICWs. Loading inactive, "caged" IP3 into cells followed by photolytic "uncaging" with UV light, thereby liberating IP3, is a well-established method to trigger [Ca(2+)]i changes in single cells that is also effective in initiating ICWs. We here describe a method to load cells with caged IP3 by local electroporation of monolayer cell cultures and to apply flash photolysis to increase intracellular IP3 and induce [Ca(2+)]i changes, or initiate ICWs. Moreover, the electroporation method allows loading of membrane-impermeable agents that interfere with IP3 and Ca(2+) signaling.
Topics: Adenosine Triphosphate; Calcium Signaling; Electroporation; Inositol 1,4,5-Trisphosphate; Photolysis
PubMed: 25734071
DOI: 10.1101/pdb.top066068